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I have a road network with paved/unpaved status in attribute table. This road network don't must contain isolated paved geometry. There are any solutions find isolated geometry in GIS software (ArcGIS/QGIS or other)? enter image description here

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So you can't have a paved without touching a unpaved one is that correct? – Nathan W Aug 2 '12 at 11:54
add picture: 'green' road - major paved road / 'red' - unpaved road / 'blue' - isolated paved roads (must be unpaved) – HasT Aug 2 '12 at 12:35
Happy to use Spatailite? – Nathan W Aug 2 '12 at 12:54
What, precisely, does "isolated" mean in this context? The pictured network is connected, so from that perspective no part of it is "isolated". If we are meant to view colors as designating subnetworks, then we see two separate blue ones labeled as paved which would be equally valid "isolated" subnetworks. If instead we view it as a union of a paved network and an unpaved network and look only for "isolated" paved subnetworks, we find three equally valid candidates among the two blue and one green sections. – whuber♦ Aug 2 '12 at 14:50
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It sounds to me like every single paved street must be connected in a single network. Any paved street not connected to that network must have been mistakenly given the "paved" attribute. – nmpeterson Aug 2 '12 at 15:03

2 Answers

up vote 2 down vote accepted

It isn't very fancy, but depending on how your line data is drawn it may work:

1) Use the Unsplit Line tool on your road file and have your dissolve field be your paved/unpaved field in your table. This means you will have one large object representing the connected paved roads.
2) Select all paved roads in the new file.
3) Manually remove the large object from the selection.
4) Change the road type of the selected roads (only those paved roads not connected to a network).
5) Split your lines again.

Or if you want your road designation to remain the same, do 1-3 and select from the original road layer the lines that intersect with the roads you have selected in your new layer.

Again, if your road networks do not have vertices in the correct places the Unsplit tool will not work correctly, but it is worth a shot.

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up vote 2 down vote

I just thought of a fairly simple solution, which assumes the comment I posted on the question is correct:

It sounds to me like every single paved street must be connected in a single network. Any paved street not connected to that network must have been mistakenly given the "paved" attribute.

If so, in ArcGIS you can use the Dissolve tool, dissolving on the attribute that contains paved/unpaved status. (Make sure the "Create Multipart Features" option is selected.)

From the dissolved feature class, you can then delete all features that are classified as unpaved (selected with an attribute query of status = unpaved), as well as the main network of paved roads (which will be a massive single feature). This should leave only the "isolated" paved roads.

From there, you can do a Select By Location on the original road feature class: any road that overlaps the isolated paved roads in the dissolved feature class can be selected.

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